How tight junctions might prevent small charged solutes from entering the brain (across the blood-brain barrier) is made clear by our new model of tight junction structure based on a lipidic backbone. Tight junctions in invertebrates also appear to have lipidic backbones though our most recent observations suggest that periodic structures, presumably proteins are intercalated into these backbones. This new work has been published. New methods depending on atomic force microscopy are under development to study junction structure in more detail. Otherwise this project is in abeyance.